2025/10/06 by Guillaume Dréau, Dréau, G., Y. Lebreton +5
Engineering · #Calibration and Measurement Techniques #FOS: Physical sciences #Infrared Target Detection Methodologies #Solar and Stellar Astrophysics (astro-ph.SR)
paper · pdf · doi:10.48550/arxiv.2510.04955
openalex publication_date 2025/10/06 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
The high-frequency resolution of the four-year Kepler time series allows detailed study of seismic modes in luminous giants. Seismic observables help infer interior structures via comparisons with stellar models. We aim to investigate differences between H-shell (Red-Giant Branch; RGB) and He-burning (red clump and Asymptotic-Giant Branch; AGB) stars in the He-II ionisation zone and the sensitivity of seismic parameters to input physics in stellar models. We used a grid of stellar models with masses 0.8-2.5M_\odot and metallicities -1.0-0.25dex, including mass loss, overshooting, thermohaline mixing, and rotation-induced mixing. P-mode frequencies were inferred by suppressing g-modes in the core. The main factors affecting seismic observables are stellar mass and metallicity. The He-II glitch amplitude in the local large frequency separation Δν correlates with the He-II ionisation zone density, explaining observed differences between RGB and clump/AGB stars. That amplitude exceeds 10% of Δν in high-luminosity giants, making the asymptotic expansion less accurate when Δν≤ 0.5 μHz. Mass loss on the RGB and rotation-induced mixing from the main sequence to the early-AGB produce phase differences in the He-II glitch modulation signature between RGB and clump/AGB stars. Efficient RGB mass loss (for M ≤ 1.5 M_\odot) and mixing processes (for M ≥ 1.5 M_\odot) leave detectable signatures in p-mode frequencies, enabling classification of red giants.